What does "Safe Migration Parallel Worker" process indicates
What does "Safe Migration Parallel Worker" process indicates under System --> Status page? Why does it shows Disabled status on fresh installed server and Ok status on upgraded server.
Safe Migration Parallel Worker is the process which takes care of the data migration which happens on backend during the upgrade. It shows Disabled on Fresh install because fresh installs don't have any data that needs to be migrated from an older database schema.
Safe Migration is called during upgrades, We leave the process online post upgrade in the background. However, it's only called during the upgrade process and will stay idle until next upgrade.